These routines return a NULL-terminated array of chtype quantities,
starting at the current cursor position in the named window and ending at the
right margin of the window. The four functions with n as
the last argument, return a leading substring at most n characters long
(exclusive of the trailing (chtype)0).
Constants defined in <curses.h> can be used with the & (logical
AND) operator to extract the character or the attribute alone from any position
in the chstr [see curs_inch(3X)].

Note that all routines except winchnstr may be macros. SVr4 does not
document whether the result string is 0-terminated; it does not document
whether a length limit argument includes any trailing 0; and it does not
document the meaning of the return value.

These functions are described in the XSI Curses standard, Issue 4. It is no
more specific than the SVr4 documentation on the trailing 0. It does specify
that the successful return of the functions is OK.